Freddy, running functions in the 3DGS like tasks in a cooperative multitasking environment (old versions of Windows). Cooperatively multitasked system must rely on each process to regularly give time to other processes on the system. A poorly designed task, or a "hung" process, can effectively bring the system to a halt.
Shure, You may use long loops without wait (for setup your level, for example). But those loops must be endable.